Preheat oven to 350°. Generously grease a 9-inch cake or springform pan with non-stick spray. Set aside.
In a large bowl combine flour, sugar, baking powder and salt. In a medium bowl, whisk eggs, ricotta, vanilla and lemon zest until smooth; fold into dry ingredients just until blended. Then stir in melted butter, followed by 1 1/2 cups blueberries, being careful not to crush berries. Scrape batter into prepared pan and scatter remaining 1/2 cup of blueberries on top.
Bake cake until edges are golden brown and a tester inserted into the center comes out clean, 50-55 minutes. Let cool at least 20 minutes before unmolding. For glaze, mix powdered sugar, melted butter and lemon juice until smooth in a measuring cup with a spout for easy pouring. Remove from pan and place on cake plate, pour glaze over top if desired.